SUPREME COURT OF THE UNITED STATES

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1 (Slip Opinion) OCTOBER TERM, Syllabus NOTE: Where it is feasible, a syllabus (headnote) will be released, as is being done in connection with this case, at the time the opinion is issued. The syllabus constitutes no part of the opinion of the Court but has been prepared by the Reporter of Decisions for the convenience of the reader. See United States v. Detroit Timber & Lumber Co., 200 U. S. 321, 337. SUPREME COURT OF THE UNITED STATES Syllabus WILLIAMS v. ILLINOIS CERTIORARI TO THE SUPREME COURT OF ILLINOIS No Argued December 6, 2011 Decided June 18, 2012 At petitioner s bench trial for rape, Sandra Lambatos, a forensic specialist at the Illinois State Police lab, testified that she matched a DNA profile produced by an outside laboratory, Cellmark, to a profile the state lab produced using a sample of petitioner s blood. She testified that Cellmark was an accredited laboratory and that business records showed that vaginal swabs taken from the victim, L. J., were sent to Cellmark and returned. She offered no other statement for the purpose of identifying the sample used for Cellmark s profile or establishing how Cellmark handled or tested the sample. Nor did she vouch for the accuracy of Cellmark s profile. The defense moved to exclude, on Confrontation Clause grounds, Lambatos testimony insofar as it implicated events at Cellmark, but the prosecution said that petitioner s confrontation rights were satisfied because he had the opportunity to cross-examine the expert who had testified as to the match. The prosecutor argued that Illinois Rule of Evidence 703 permitted an expert to disclose facts on which the expert s opinion is based even if the expert is not competent to testify to those underlying facts, and that any deficiency went to the weight of the evidence, not its admissibility. The trial court admitted the evidence and found petitioner guilty. Both the Illinois Court of Appeals and the State Supreme Court affirmed, concluding that Lambatos testimony did not violate petitioner s confrontation rights because Cellmark s report was not offered into evidence to prove the truth of the matter asserted. Held: The judgment is affirmed. 238 Ill. 2d 125, 939 N. E. 2d 268, affirmed. JUSTICE ALITO, joined by THE CHIEF JUSTICE, JUSTICE KENNEDY, and JUSTICE BREYER, concluded that the form of expert testimony given in this case does not violate the Confrontation Clause. Pp

2 2 WILLIAMS v. ILLINOIS Syllabus (a) Before Crawford v. Washington, 541 U. S. 36, this Court took the view that the Confrontation Clause did not bar the admission of out-of-court statements that fell within a firmly rooted exception to the hearsay rule. In Crawford, the Court held that such statements could be admitted only where the declarant is unavailable, and only where the defendant has had a prior opportunity to cross-examine. Id., at 59. In both Melendez-Diaz v. Massachusetts, 557 U. S. 305, and Bullcoming v. New Mexico, 564 U. S., two of the many cases that have arisen from Crawford, this Court ruled that scientific reports could not be used as substantive evidence against a defendant unless the analyst who prepared and certified the report was subject to confrontation. In each case, the report at issue contain[ed] a testimonial certification, made in order to prove a fact at a criminal trial. 564 U. S., at. Here, in contrast, the question is the constitutionality of allowing an expert witness to discuss others testimonial statements if those statements are not themselves admitted as evidence. Pp (b) An expert witness may voice an opinion based on facts concerning the events at issue even if the expert lacks first-hand knowledge of those facts. A long tradition in American courts permits an expert to testify in the form of a hypothetical question, where the expert assumes the truth of factual predicates and then offers testimony based on those assumptions. See Forsyth v. Doolittle, 120 U. S. 73, 77. Modern evidence rules dispense with the need for hypothetical questions and permit an expert to base an opinion on facts made known to the expert at or before the hearing, though such reliance does not constitute admissible evidence of the underlying information. Ill. Rule Evid. 703; Fed. Rule Evid Both Illinois and Federal Rules bar an expert from disclosing the inadmissible evidence in jury trials but not in bench trials. This is important because Crawford, while departing from prior Confrontation Clause precedent in other respects, reaffirmed the proposition that the Clause does not bar the use of testimonial statements for purposes other than establishing the truth of the matter asserted. 541 U. S., at 59, n. 9. Pp (c) For Confrontation Clause purposes, the references to Cellmark in the trial record either were not hearsay or were not offered for the truth of the matter asserted. Pp (1) Petitioner s confrontation right was not violated when Lambatos answered yes to a question about whether there was a match between the DNA profile found in semen from the vaginal swabs of [L. J.] and the one identified as petitioner s. Under Illinois law, this putatively offending phrase was not admissible for the purpose of proving the truth of the matter asserted i.e., that the matching

3 Cite as: 567 U. S. (2012) 3 Syllabus DNA profile was found in semen from the vaginal swabs. Rather, that fact was a mere premise of the prosecutor s question, and Lambatos simply assumed it to be true in giving her answer. Because this was a bench trial, the Court assumes that the trial judge understood that the testimony was not admissible to prove the truth of the matter asserted. It is also unlikely that the judge took the testimony as providing chain-of-custody evidence. The record does not support such an understanding; no trial judge is likely to be so confused; and the admissible evidence left little room for argument that Cellmark s sample came from any source but L. J. s swabs, since the profile matched the very man she identified in a lineup and at trial as her attacker. Pp (2) Nor did the substance of Cellmark s report need to be introduced in order to show that Cellmark s profile was based on the semen in L. J. s swabs or that its procedures were reliable. The issue here is whether petitioner s confrontation right was violated, not whether the State offered sufficient foundational evidence to support the admission of Lambatos opinion. If there were no proof that Cellmark s profile was accurate, Lambatos testimony would be irrelevant, but the Confrontation Clause bars not the admission of irrelevant evidence, but the admission of testimonial statements by declarants who are not subject to cross-examination. Here, the trial record does not lack admissible evidence with respect to the source of the sample tested by Cellmark or the reliability of its profile. The State offered conventional chain-of-custody evidence, and the match between Cellmark s profile and petitioner s was telling confirmation that Cellmark s profile was deduced from the semen on L. J. s swabs. The match also provided strong circumstantial evidence about the reliability of Cellmark s work. Pp (3) This conclusion is consistent with Bullcoming and Melendez- Diaz, where forensic reports were introduced for the purpose of proving the truth of what they asserted. In contrast, Cellmark s report was considered for the limited purpose of seeing whether it matched something else, and the relevance of that match was established by independent circumstantial evidence showing that the report was based on a sample from the crime scene. There are at least four safeguards to prevent abuses in such situations. First, trial courts can screen out experts who would act as conduits for hearsay by strictly enforcing the requirement that experts display genuine scientific, technical, or other specialized knowledge to help the trier of fact understand the evidence or determine a fact at issue. Fed. Rule Evid. 702(a). Second, experts are generally precluded from disclosing inadmissible evidence to a jury. Third, if such evidence is disclosed, a trial judge may instruct the jury that the statements cannot be ac-

4 4 WILLIAMS v. ILLINOIS Syllabus cepted for their truth, and that an expert s opinion is only as good as the independent evidence establishing its underlying premises. Fourth, if the prosecution cannot muster independent admissible evidence to prove foundational facts, the expert s testimony cannot be given weight by the trier of fact. Pp (e) Even if Cellmark s report had been introduced for its truth, there would have been no Confrontation Clause violation. The Clause refers to testimony by witnesses against an accused, prohibiting modern-day practices that are tantamount to the abuses that gave rise to the confrontation right, namely, (a) out-of-court statements having the primary purpose of accusing a targeted individual of engaging in criminal conduct, and (b) formalized statements such as affidavits, depositions, prior testimony, or confessions. These characteristics were present in every post-crawford case in which a Confrontation Clause violation has been found, except for Hammon v. Indiana, 547 U. S But, even in Hammon, the particular statement, elicited during police interrogation, had the primary purpose of accusing a targeted individual. A person who makes a statement to resolve an ongoing emergency is not like a trial witness because the declarant s purpose is to bring an end to an ongoing threat. Michigan v. Bryant, 562 U. S.,. Such a statement s admissibility is the concern of... rules of evidence, not the Confrontation Clause. Id.,. The forensic reports in Melendez-Diaz and Bullcoming ran afoul of the Confrontation Clause because they were the equivalent of affidavits made for the purpose of proving a particular criminal defendant s guilt. But the Cellmark report s primary purpose was to catch a dangerous rapist who was still at large, not to obtain evidence for use against petitioner, who was neither in custody nor under suspicion at that time. Nor could anyone at Cellmark possibly know that the profile would inculpate petitioner. There was thus no prospect of fabrication and no incentive to produce anything other than a scientifically sound and reliable profile. Bryant, supra, at,. Lab technicians producing a DNA profile generally have no way of knowing whether it will turn out to be incriminating, exonerating, or both. And with numerous technicians working on a profile, it is likely that each technician s sole purpose is to perform a task in accordance with accepted procedures. The knowledge that defects in a DNA profile may be detected from the profile itself provides a further safeguard. Pp JUSTICE THOMAS concluded that the disclosure of Cellmark s out-ofcourt statements through Lambatos expert testimony did not violate the Confrontation Clause solely because Cellmark s statements lacked the requisite formality and solemnity to be considered testimonial, see Michigan v. Bryant, 562 U. S., (THOMAS, J.,

5 Cite as: 567 U. S. (2012) 5 Syllabus concurring in judgment). Pp (a) There was no plausible reason for the introduction of Cellmark s statements other than to establish their truth. Pp (1) Illinois Rule of Evidence 703 permits an expert to base his opinion on facts about which he lacks personal knowledge and to disclose those facts to the trier of fact. Under Illinois law, such facts are not admitted for their truth, but only to explain the basis of the expert s opinion. See People v. Pasch, 152 Ill. 2d 133. But state evidence rules do not trump a defendant s constitutional right to confrontation. This Court ensures that an out-of-court statement was introduced for a legitimate, nonhearsay purpose before relying on the not-for-its-truth rationale to dismiss the Confrontation Clause s application. See Tennessee v. Street, 471 U. S. 409, 417. Statements introduced to explain the basis of an expert s opinion are not introduced for a plausible nonhearsay purpose because, to use the basis testimony in evaluating the expert s opinion, the factfinder must consider the truth of the basis testimony. This commonsense conclusion is not undermined by any historical practice exempting expert basis testimony from the rigors of the Confrontation Clause. Before the Federal Rules of Evidence were adopted in 1975, an expert could render an opinion based only on facts that the expert had personally perceived or learned at trial. In 1975, that universe of facts was expanded to include facts that the expert learned out of court by means other than his own perception. The disclosure of such facts raises Confrontation Clause concerns. Pp (2) Those concerns are fully applicable here. In concluding that petitioner s DNA profile matched the profile derived from L. J. s swabs, Lambatos relied on Cellmark s out-of-court statements that its profile was in fact derived from those swabs, rather than from some other source. Thus, the validity of Lambatos opinion ultimately turned on the truth of Cellmark s statements. Pp (b) These statements, however, were not testimonial for purposes of the Confrontation Clause, which applies to witnesses against the accused in other words, those who bear testimony. Crawford v. Washington, 541 U. S. 36, 51. Testimony, in turn, is [a] solemn declaration or affirmation made for the purpose of establishing or proving some fact. Ibid. In light of its text, the Confrontation Clause regulates only the use of statements bearing indicia of solemnity. Davis v. Washington, 547 U. S. 813, , 840 (opinion of THOMAS, J.). This test comports with history because solemnity marked the practices that the Confrontation Clause was designed to eliminate, namely, the ex parte examination of witnesses under English bail and committal statutes. See id., at 835. Accordingly, the Clause reaches formalized testimonial materials, such as deposi-

6 6 WILLIAMS v. ILLINOIS Syllabus tions, affidavits, and prior testimony, or statements resulting from formalized dialogue, such as custodial interrogation. Bryant, supra, at. Applying these principles, Cellmark s report is not a statement by a witnes[s] under the Confrontation Clause. It lacks the solemnity of an affidavit or deposition, for it is neither a sworn nor a certified declaration of fact. And, although it was produced at the request of law enforcement, it was not the product of formalized dialogue resembling custodial interrogation. Melendez-Diaz, 557 U. S. 305, and Bullcoming v. New Mexico, 564 U. S., distinguished. Pp ALITO, J., announced the judgment of the Court and delivered an opinion, in which ROBERTS, C. J., and KENNEDY and BREYER, JJ., joined. BREYER, J., filed a concurring opinion. THOMAS, J., filed an opinion concurring in the judgment. KAGAN, J., filed a dissenting opinion, in which SCALIA, GINSBURG, and SOTOMAYOR, JJ., joined.

7 Cite as: 567 U. S. (2012) 1 Opinion of ALITO, J. NOTICE: This opinion is subject to formal revision before publication in the preliminary print of the United States Reports. Readers are requested to notify the Reporter of Decisions, Supreme Court of the United States, Washington, D. C , of any typographical or other formal errors, in order that corrections may be made before the preliminary print goes to press. SUPREME COURT OF THE UNITED STATES No SANDY WILLIAMS, PETITIONER v. ILLINOIS ON WRIT OF CERTIORARI TO THE SUPREME COURT OF ILLINOIS [June 18, 2012] JUSTICE ALITO announced the judgment of the Court and delivered an opinion, in which THE CHIEF JUSTICE, JUSTICE KENNEDY, and JUSTICE BREYER join. In this case, we decide whether Crawford v. Washington, 541 U. S. 36, 50 (2004), precludes an expert witness from testifying in a manner that has long been allowed under the law of evidence. Specifically, does Crawford bar an expert from expressing an opinion based on facts about a case that have been made known to the expert but about which the expert is not competent to testify? We also decide whether Crawford substantially impedes the ability of prosecutors to introduce DNA evidence and thus may effectively relegate the prosecution in some cases to reliance on older, less reliable forms of proof. In petitioner s bench trial for rape, the prosecution called an expert who testified that a DNA profile produced by an outside laboratory, Cellmark, matched a profile produced by the state police lab using a sample of petitioner s blood. On direct examination, the expert testified that Cellmark was an accredited laboratory and that Cellmark provided the police with a DNA profile. The expert also explained the notations on documents admit-

8 2 WILLIAMS v. ILLINOIS Opinion of ALITO, J. ted as business records, stating that, according to the records, vaginal swabs taken from the victim were sent to and received back from Cellmark. The expert made no other statement that was offered for the purpose of identifying the sample of biological material used in deriving the profile or for the purpose of establishing how Cellmark handled or tested the sample. Nor did the expert vouch for the accuracy of the profile that Cellmark produced. Nevertheless, petitioner contends that the expert s testimony violated the Confrontation Clause as interpreted in Crawford. Petitioner s main argument is that the expert went astray when she referred to the DNA profile provided by Cellmark as having been produced from semen found on the victim s vaginal swabs. But both the Illinois Appellate Court and the Illinois Supreme Court found that this statement was not admitted for the truth of the matter asserted, and it is settled that the Confrontation Clause does not bar the admission of such statements. See id., at 59 60, n. 9 (citing Tennessee v. Street, 471 U. S. 409 (1985)). For more than 200 years, the law of evidence has permitted the sort of testimony that was given by the expert in this case. Under settled evidence law, an expert may express an opinion that is based on facts that the expert assumes, but does not know, to be true. It is then up to the party who calls the expert to introduce other evidence establishing the facts assumed by the expert. While it was once the practice for an expert who based an opinion on assumed facts to testify in the form of an answer to a hypothetical question, modern practice does not demand this formality and, in appropriate cases, permits an expert to explain the facts on which his or her opinion is based without testifying to the truth of those facts. See Fed. Rule Evid That is precisely what occurred in this case, and we should not lightly swee[p] away an accepted rule governing the admission of scientific evi-

9 Cite as: 567 U. S. (2012) 3 Opinion of ALITO, J. dence. Melendez-Diaz v. Massachusetts, 557 U. S. 305, 330 (2009) (KENNEDY, J., dissenting). We now conclude that this form of expert testimony does not violate the Confrontation Clause because that provision has no application to out-of-court statements that are not offered to prove the truth of the matter asserted. When an expert testifies for the prosecution in a criminal case, the defendant has the opportunity to cross-examine the expert about any statements that are offered for their truth. Out-of-court statements that are related by the expert solely for the purpose of explaining the assumptions on which that opinion rests are not offered for their truth and thus fall outside the scope of the Confrontation Clause. Applying this rule to the present case, we conclude that the expert s testimony did not violate the Sixth Amendment. As a second, independent basis for our decision, we also conclude that even if the report produced by Cellmark had been admitted into evidence, there would have been no Confrontation Clause violation. The Cellmark report is very different from the sort of extrajudicial statements, such as affidavits, depositions, prior testimony, and confessions, that the Confrontation Clause was originally understood to reach. The report was produced before any suspect was identified. The report was sought not for the purpose of obtaining evidence to be used against petitioner, who was not even under suspicion at the time, but for the purpose of finding a rapist who was on the loose. And the profile that Cellmark provided was not inherently inculpatory. On the contrary, a DNA profile is evidence that tends to exculpate all but one of the more than 7 billion people in the world today. The use of DNA evidence to exonerate persons who have been wrongfully accused or convicted is well known. If DNA profiles could not be introduced without calling the technicians who participated in the preparation of the profile, economic

10 4 WILLIAMS v. ILLINOIS Opinion of ALITO, J. pressures would encourage prosecutors to forgo DNA testing and rely instead on older forms of evidence, such as eyewitness identification, that are less reliable. See Perry v. New Hampshire, 565 U. S. (2012). The Confrontation Clause does not mandate such an undesirable development. This conclusion will not prejudice any defendant who really wishes to probe the reliability of the DNA testing done in a particular case because those who participated in the testing may always be subpoenaed by the defense and questioned at trial. I A On February 10, 2000, in Chicago, Illinois, a young woman, L. J., was abducted while she was walking home from work. The perpetrator forced her into his car and raped her, then robbed her of her money and other personal items and pushed her out into the street. L. J. ran home and reported the attack to her mother, who called the police. An ambulance took L. J. to the hospital, where doctors treated her wounds and took a blood sample and vaginal swabs for a sexual-assault kit. A Chicago Police detective collected the kit, labeled it with an inventory number, and sent it under seal to the Illinois State Police (ISP) lab. At the ISP lab, a forensic scientist received the sealed kit. He conducted a chemical test that confirmed the presence of semen on the vaginal swabs, and he then resealed the kit and placed it in a secure evidence freezer. During the period in question, the ISP lab often sent biological samples to Cellmark Diagnostics Laboratory in Germantown, Maryland, for DNA testing. There was evidence that the ISP lab sent L. J. s vaginal swabs to Cellmark for testing and that Cellmark sent back a report containing a male DNA profile produced from semen taken from those swabs. At this time, petitioner was not under

11 Cite as: 567 U. S. (2012) 5 Opinion of ALITO, J. suspicion for L. J. s rape. Sandra Lambatos, a forensic specialist at the ISP lab, conducted a computer search to see if the Cellmark profile matched any of the entries in the state DNA database. The computer showed a match to a profile produced by the lab from a sample of petitioner s blood that had been taken after he was arrested on unrelated charges on August 3, On April 17, 2001, the police conducted a lineup at which L. J. identified petitioner as her assailant. Petitioner was then indicted for aggravated criminal sexual assault, aggravated kidnaping, and aggravated robbery. In lieu of a jury trial, petitioner chose to be tried before a state judge. B Petitioner s bench trial began in April In open court, L. J. again identified petitioner as her attacker. The State also offered three expert forensic witnesses to link petitioner to the crime through his DNA. First, Brian Hapack, an ISP forensic scientist, testified that he had confirmed the presence of semen on the vaginal swabs taken from L. J. by performing an acid phosphatase test. After performing this test, he testified, he resealed the evidence and left it in a secure freezer at the ISP lab. Second, Karen Abbinanti, a state forensic analyst, testified that she had used Polymerase Chain Reaction (PCR) and Short Tandem Repeat (STR) techniques to develop a DNA profile from a blood sample that had been drawn from petitioner after he was arrested in August She also stated that she had entered petitioner s DNA profile into the state forensic database. Third, the State offered Sandra Lambatos as an expert witness in forensic biology and forensic DNA analysis. On direct examination, Lambatos testified about the general process of using the PCR and STR techniques to generate

12 6 WILLIAMS v. ILLINOIS Opinion of ALITO, J. DNA profiles from forensic samples such as blood and semen. She then described how these DNA profiles could be matched to an individual based on the individual s unique genetic code. In making a comparison between two DNA profiles, Lambatos stated, it is a commonly accepted practice within the scientific community for one DNA expert to rely on the records of another DNA expert. App. 51. Lambatos also testified that Cellmark was an accredited crime lab and that, in her experience, the ISP lab routinely sent evidence samples via Federal Express to Cellmark for DNA testing in order to expedite the testing process and to reduce [the lab s] backlog. Id., at To keep track of evidence samples and preserve the chain of custody, Lambatos stated, she and other analysts relied on sealed shipping containers and labeled shipping manifests, and she added that experts in her field regularly relied on such protocols. Id., at Lambatos was shown shipping manifests that were admitted into evidence as business records, and she explained what they indicated, namely, that the ISP lab had sent L. J. s vaginal swabs to Cellmark, and that Cellmark had sent them back, along with a deduced male DNA profile. Id., at The prosecutor asked Lambatos whether there was a computer match between the male DNA profile found in semen from the vaginal swabs of [L. J.] and [the] male DNA profile that had been identified from petitioner s blood sample. Id., at 55. The defense attorney objected to this question for lack of foundation, arguing that the prosecution had offered no evidence with regard to any testing that s been done to generate a DNA profile by another lab to be testified to by this witness. Ibid. The prosecutor responded: I m not getting at what another lab did. Id., at 56. Rather, she said, she was simply asking Lambatos about her own testing based on [DNA] information that she had received from Cellmark.

13 Cite as: 567 U. S. (2012) 7 Opinion of ALITO, J. Ibid. The trial judge agreed, noting, If she says she didn t do her own testing and she relied on a test of another lab and she s testifying to that, we will see what she s going to say. Ibid. The prosecutor then proceeded, asking Lambatos, Did you compare the semen that had been identified by Brian Hapack from the vaginal swabs of [L. J.] to the male DNA profile that had been identified by Karen [Abbinanti] from the blood of [petitioner]? Ibid. Lambatos answered Yes. Ibid. Defense counsel lodged an objection to the form of the question, but the trial judge overruled it. Ibid. Lambatos then testified that, based on her own comparison of the two DNA profiles, she concluded that [petitioner] cannot be excluded as a possible source of the semen identified in the vaginal swabs, and that the probability of the profile s appearing in the general population was 1 in 8.7 quadrillion black, 1 in 390 quadrillion white, or 1 in 109 quadrillion Hispanic unrelated individuals. Id., at 57. Asked whether she would call this a match to [petitioner], Lambatos answered yes, again over defense counsel s objection. Id., at 58. The Cellmark report itself was neither admitted into evidence nor shown to the factfinder. Lambatos did not quote or read from the report; nor did she identify it as the source of any of the opinions she expressed. On cross-examination, Lambatos confirmed that she did not conduct or observe any of the testing on the vaginal swabs, and that her testimony relied on the DNA profile produced by Cellmark. Id., at 59. She stated that she trusted Cellmark to do reliable work because it was an accredited lab, but she admitted she had not seen any of the calibrations or work that Cellmark had done in deducing a male DNA profile from the vaginal swabs. Id., at Asked whether the DNA sample might have been de-

14 8 WILLIAMS v. ILLINOIS Opinion of ALITO, J. graded before Cellmark analyzed it, Lambatos answered that, while degradation was technically possible, she strongly doubted it had occurred in this case. She gave two reasons. First, the ISP lab likely would have noticed the degradation before sending the evidence off to Cellmark. Second, and more important, Lambatos also noted that the data making up the DNA profile would exhibit certain telltale signs if it had been deduced from a degraded sample: The visual representation of the DNA sequence would exhibit specific patterns of degradation, and she didn t see any evidence of that from looking at the profile that Cellmark produced. Id., at When Lambatos finished testifying, the defense moved to exclude her testimony with regards to testing done by [Cellmark] based on the Confrontation Clause. Id., at 90. Defense counsel argued that there was no evidence with regards to... any work done by [Cellmark] to justify testimony coming into this case with regard to their analysis. Ibid. Thus, while defense counsel objected to and sought the exclusion of Lambatos testimony insofar as it implicated events at the Cellmark lab, defense counsel did not object to or move for the exclusion of any other portion of Lambatos testimony, including statements regarding the contents of the shipment sent to or received back from Cellmark. See id., at 55, 56, 90. See also 385 Ill. App. 3d 359, , 895 N. E. 2d 961, 968 (2008) (chain-ofcustody argument based on shipping manifests waived). The prosecution responded that petitioner s Confrontation Clause rights were satisfied because he had the opportunity to cross-examine the expert who had testified that there was a match between the DNA profiles produced by Cellmark and Abbinanti. App. 91. Invoking Illinois Rule of Evidence 703, 1 the prosecutor argued that 1 Consistent with the Federal Rules, Illinois Rule of Evidence 703 provides as follows:

15 Cite as: 567 U. S. (2012) 9 Opinion of ALITO, J. an expert is allowed to disclose the facts on which the expert s opinion is based even if the expert is not competent to testify to those underlying facts. She further argued that any deficiency in the foundation for the expert s opinion [d]oesn t go to the admissibility of [that] testimony, but instead goes to the weight of the testimony. App. 91. The trial judge agreed with the prosecution and stated that the issue is... what weight do you give the test, not do you exclude it. Id., at 94. Accordingly, the judge stated that he would not exclude Lambatos testimony, which was based on her own independent testing of the data received from [Cellmark]. Id., at (alteration in original). The trial court found petitioner guilty of the charges against him. The state court of appeals affirmed in relevant part, concluding that Lambatos testimony did not violate petitioner s confrontation rights because the Cellmark report was not offered into evidence to prove the truth of the matter it asserted. See 385 Ill. App. 3d, at 369, 895 N. E. 2d, at ( Cellmark s report was not offered for the truth of the matter asserted; rather, it was offered to provide a basis for Lambatos opinion ) The Supreme Court of Illinois also affirmed. 238 Ill. 2d 125, 939 N. E. 2d 268 (2010). Under state law, the court noted, the Cellmark report could not be used as substantive evidence. When Lambatos referenced the report during her direct examination, she did so for the limited purpose of explaining the basis for [her expert opinion], not for the purpose of showing the truth of the matter asserted by The facts or data in the particular case upon which an expert bases an opinion or inference may be those perceived by or made known to the expert at or before the hearing. If of a type reasonably relied upon by experts in the particular field in forming opinions or inferences upon the subject, the facts or data need not be admissible in evidence.

16 10 WILLIAMS v. ILLINOIS Opinion of ALITO, J. the report. Id., at 150, 939 N. E. 2d, at 282. Thus, the report was not used to establish its truth, but only to show the underlying facts and data Lambatos used before rendering an expert opinion. Id., at 145, 939 N. E. 2d, at 279. We granted certiorari. 564 U. S. (2011). II A The Confrontation Clause of the Sixth Amendment provides that, [i]n all criminal prosecutions, the accused shall enjoy the right... to be confronted with the witnesses against him. Before Crawford, this Court took the view that the Confrontation Clause did not bar the admission of an out-of-court statement that fell within a firmly rooted exception to the hearsay rule, see Ohio v. Roberts, 448 U. S. 56, 66 (1980), but in Crawford, the Court adopted a fundamentally new interpretation of the confrontation right, holding that [t]estimonial statements of witnesses absent from trial [can be] admitted only where the declarant is unavailable, and only where the defendant has had a prior opportunity to cross-examine. 541 U. S., at 59. Crawford has resulted in a steady stream of new cases in this Court. See Bullcoming v. New Mexico, 564 U. S. (2011); Michigan v. Bryant, 562 U. S. (2011); Melendez-Diaz, 557 U. S. 305; Giles v. California, 554 U. S. 353 (2008); Indiana v. Edwards, 554 U. S. 164 (2008); Davis v. Washington, 547 U. S. 813 (2006). Two of these decisions involved scientific reports. In Melendez-Diaz, the defendant was arrested and charged with distributing and trafficking in cocaine. At trial, the prosecution introduced bags of a white powdery substance that had been found in the defendant s possession. The trial court also admitted into evidence three certificates of analysis from the state forensic laboratory stating that the bags had been examined with the following results:

17 Cite as: 567 U. S. (2012) 11 Opinion of ALITO, J. The substance was found to contain: Cocaine. 557 U. S., at 308 (internal quotation marks omitted). The Court held that the admission of these certificates, which were executed under oath before a notary, violated the Sixth Amendment. They were created for the sole purpose of providing evidence against a defendant, id., at 323, and were quite plainly affidavits, id., at 330 (THOMAS, J., concurring). The Court emphasized that the introduction of the report to prove the nature of the substance found in the defendant s possession was tantamount to live, in-court testimony on that critical fact and that the certificates did precisely what a witness does on direct examination. Id., at 311 (internal quotation marks omitted). There was no doubt that the certificates were used to prove the truth of the matter they asserted. Under state law, the sole purpose of the affidavits was to provide prima facie evidence of the composition, quality, and the net weight of the analyzed substance. Ibid. (internal quotation marks omitted and emphasis deleted). On these facts, the Court said, it was clear that the certificates were testimonial statements that could not be introduced unless their authors were subjected to the crucible of cross-examination. Id., at 311, 317 (quoting Crawford, supra, at 61). In Bullcoming, we held that another scientific report could not be used as substantive evidence against the defendant unless the analyst who prepared and certified the report was subject to confrontation. The defendant in that case had been convicted of driving while intoxicated. At trial, the court admitted into evidence a forensic report certifying that a sample of the defendant s blood had an alcohol concentration of 0.21 grams per hundred milliliters, well above the legal limit. Instead of calling the analyst who signed and certified the forensic report, the prosecution called another analyst who had not performed or observed the actual analysis, but was only familiar with

18 12 WILLIAMS v. ILLINOIS Opinion of ALITO, J. the general testing procedures of the laboratory. The Court declined to accept this surrogate testimony, despite the fact that the testifying analyst was a knowledgeable representative of the laboratory who could explain the lab s processes and the details of the report. 564 U. S., at (KENNEDY, J., dissenting) (slip op., at 1). The Court stated simply: The accused s right is to be confronted with the analyst who made the certification. Id., at (slip op., at 2). Just as in Melendez-Diaz, the forensic report that was introduce[d] in Bullcoming contain[ed] a testimonial certification, made in order to prove a fact at a criminal trial. 564 U. S., at (slip op., at 7 8). The report was signed by the nontestifying analyst who had authored it, stating, I certify that I followed the procedures set out on the reverse of this report, and the statements in this block are correct. The concentration of alcohol in this sample is based on the grams of alcohol in one hundred milliliters of blood. App. in Bullcoming, O. T. 2010, No , p. 62. Critically, the report was introduced at trial for the substantive purpose of proving the truth of the matter asserted by its out-of-court author namely, that the defendant had a blood-alcohol level of This was the central fact in question at the defendant s trial, and it was dispositive of his guilt. In concurrence, JUSTICE SOTOMAYOR highlighted the importance of the fact that the forensic report had been admitted into evidence for the purpose of proving the truth of the matter it asserted. She emphasized that this [was] not a case in which an expert witness was asked for his independent opinion about underlying testimonial reports that were not themselves admitted into evidence. 564 U. S., at (slip op., at 6) (opinion concurring in part) (citing Fed. Rule Evid. 703). We would face a different question, she observed, if asked to determine the constitutionality of allowing an expert witness to discuss others

19 Cite as: 567 U. S. (2012) 13 Opinion of ALITO, J. testimonial statements if the testimonial statements were not themselves admitted as evidence. Id., at (slip op., at 6). We now confront that question. B It has long been accepted that an expert witness may voice an opinion based on facts concerning the events at issue in a particular case even if the expert lacks firsthand knowledge of those facts. At common law, courts developed two ways to deal with this situation. An expert could rely on facts that had already been established in the record. But because it was not always possible to proceed in this manner, and because record evidence was often disputed, courts developed the alternative practice of allowing an expert to testify in the form of a hypothetical question. Under this approach, the expert would be asked to assume the truth of certain factual predicates, and was then asked to offer an opinion based on those assumptions. See 1 K. Broun, McCormick on Evidence 14, p. 87 (6th ed. 2006); 1 J. Wigmore, Evidence 677, p (2d ed. 1923) ( If the witness is skilled enough, his opinion may be adequately obtained upon hypothetical data alone; and it is immaterial whether he has ever seen the person, place or thing in question (citation omitted)). The truth of the premises could then be established through independent evidence, and the factfinder would regard the expert s testimony to be only as credible as the premises on which it was based. An early example of this approach comes from the English case of Beckwith v. Sydebotham, 1 Camp. 116, 170 Eng. Rep. 897 (K. B. 1807), where a party sought to prove the seaworthiness of a ship, the Earl of Wycombe, by calling as witnesses several eminent surveyors of ships who had never seen the Earl of Wycombe. Ibid. The opposing party objected to the testimony because it relied

20 14 WILLIAMS v. ILLINOIS Opinion of ALITO, J. on facts that were not known to be true, but the judge disagreed. Because the experts were peculiarly acquainted with a matter of skill or science, the judge said, the jury might be assisted by their hypothetical opinion based on certain assumed facts. Id., at 117, 170 Eng. Rep., at 897. The judge acknowledged the danger of the jury s being unduly prejudiced by wrongly assuming the truth of the hypothetical facts, but the judge noted that the experts could be asked on cross-examination what their opinion of the ship s seaworthiness would be if different hypothetical facts were assumed. If the party that had called the experts could not independently prove the truth of the premises they posited, then the experts opinion might not go for much; but still it was admissible evidence. Ibid. There is a long tradition of the use of hypothetical questions in American courts. In 1887, for example, this Court indicated its approval of the following jury instruction: As to the questions, you must understand that they are not evidence; they are mere statements to these witnesses... and, upon the hypothesis or assumption of these questions the witnesses are asked to give their [opinion]. You must readily see that the value of the answers to these questions depends largely, if not wholly, upon the fact whether the statements made in these questions are sustained by the proof. If the statements in these questions are not supported by the proof, then the answers to the questions are entitled to no weight, because based upon false assumptions or statements of facts. Forsyth v. Doolittle, 120 U. S. 73, 77 (internal quotation marks omitted). Modern rules of evidence continue to permit experts to express opinions based on facts about which they lack personal knowledge, but these rules dispense with the need for hypothetical questions. Under both the Illinois

21 Cite as: 567 U. S. (2012) 15 Opinion of ALITO, J. and the Federal Rules of Evidence, an expert may base an opinion on facts that are made known to the expert at or before the hearing, but such reliance does not constitute admissible evidence of this underlying information. Ill. Rule Evid. 703; Fed. Rule Evid Accordingly, in jury trials, both Illinois and federal law generally bar an expert from disclosing such inadmissible evidence. 2 In bench trials, however, both the Illinois and the Federal Rules place no restriction on the revelation of such information to the factfinder. When the judge sits as the trier of fact, it is presumed that the judge will understand the limited reason for the disclosure of the underlying inadmissible information and will not rely on that information for any improper purpose. As we have noted, [i]n bench trials, judges routinely hear inadmissible evidence that they are presumed to ignore when making decisions. Harris v. Rivera, 454 U. S. 339, 346 (1981) (per curiam). There is a well-established presumption that the judge [has] adhered to basic rules of procedure, when the judge is acting as a factfinder. Id., at (emphasis added). See also Gentile v. State Bar of Nev., 501 U. S. 1030, 1078 (1991) (Rehnquist, C. J., dissenting). This feature of Illinois and federal law is important because Crawford, while departing from prior Confrontation Clause precedent in other respects, took pains to reaffirm the proposition that the Confrontation Clause does not bar the use of testimonial statements for purposes 2 But disclosure of these facts or data to the jury is permitted if the value of disclosure substantially outweighs [any] prejudicial effect, Fed. Rule Evid. 703, or the probative value... outweighs the risk of unfair prejudice. People v. Pasch, 152 Ill. 2d 133, 223, 604 N. E. 2d 294, 333 (1992). When this disclosure occurs, the underlying facts are revealed to the jury for the limited purpose of explaining the basis for [the expert s] opinion and not for the truth of the matter asserted. Id., at 176, 604 N. E. 2d, at 311.

22 16 WILLIAMS v. ILLINOIS Opinion of ALITO, J. other than establishing the truth of the matter asserted. 541 U. S., at 59 60, n. 9 (citing Tennessee v. Street, 471 U. S. 409). In Street, the defendant claimed that the police had coerced him into adopting the confession of his alleged accomplice. The prosecution sought to rebut this claim by showing that the defendant s confession differed significantly from the accomplice s. Although the accomplice s confession was clearly a testimonial statement, the Court held that the jurors could hear it as long as they were instructed to consider that confession not for its truth, but only for the distinctive and limited purpose of comparing it to the defendant s confession, to see whether the two were identical. Id., at 417. III A In order to assess petitioner s Confrontation Clause argument, it is helpful to inventory exactly what Lambatos said on the stand about Cellmark. She testified to the truth of the following matters: Cellmark was an accredited lab, App. 49; the ISP occasionally sent forensic samples to Cellmark for DNA testing, ibid.; according to shipping manifests admitted into evidence, the ISP lab sent vaginal swabs taken from the victim to Cellmark and later received those swabs back from Cellmark, id., at 52 55; and, finally, the Cellmark DNA profile matched a profile produced by the ISP lab from a sample of petitioner s blood, id., at Lambatos had personal knowledge of all of these matters, and therefore none of this testimony infringed petitioner s confrontation right. Lambatos did not testify to the truth of any other matter concerning Cellmark. She made no other reference to the Cellmark report, which was not admitted into evidence and was not seen by the trier of fact. Nor did she testify to anything that was done at the Cellmark lab, and she did not vouch for the quality of Cellmark s work.

23 Cite as: 567 U. S. (2012) 17 Opinion of ALITO, J. B The principal argument advanced to show a Confrontation Clause violation concerns the phrase that Lambatos used when she referred to the DNA profile that the ISP lab received from Cellmark. This argument is developed most fully in the dissenting opinion, and therefore we refer to the dissent s discussion of this issue. In the view of the dissent, the following is the critical portion of Lambatos testimony, with the particular words that the dissent finds objectionable italicized: Q Was there a computer match generated of the male DNA profile found in semen from the vaginal swabs of [L.J.] to a male DNA profile that had been identified as having originated from Sandy Williams? A Yes, there was. Post, at 7 (opinion of KAGAN, J.) (quoting App. 56; emphasis added). According to the dissent, the italicized phrase violated petitioner s confrontation right because Lambatos lacked personal knowledge that the profile produced by Cellmark was based on the vaginal swabs taken from the victim, L. J. As the dissent acknowledges, there would have been nothing wrong with Lambatos s testifying that two DNA profiles the one shown in the Cellmark report and the one derived from Williams s blood matched each other; that was a straightforward application of Lambatos s expertise. Post, at 12. Thus, if Lambatos testimony had been slightly modified as follows, the dissent would see no problem: Q Was there a computer match generated of the male DNA profile produced by

24 18 WILLIAMS v. ILLINOIS Opinion of ALITO, J. Cellmark found in semen from the vaginal swabs of [L.J.] to a male DNA profile that had been identified as having originated from Sandy Williams? A Yes, there was. 3 The defect in this argument is that under Illinois law (like federal law) it is clear that the putatively offending phrase in Lambatos testimony was not admissible for the purpose of proving the truth of the matter asserted i.e., that the matching DNA profile was found in semen from the vaginal swabs. Rather, that fact was a mere premise of the prosecutor s question, and Lambatos simply assumed that premise to be true when she gave her answer indicating that there was a match between the two DNA profiles. There is no reason to think that the trier of fact took Lambatos answer as substantive evidence to establish where the DNA profiles came from. The dissent s argument would have force if petitioner had elected to have a jury trial. In that event, there would have been a danger of the jury s taking Lambatos testimony as proof that the Cellmark profile was derived from the sample obtained from the victim s vaginal swabs. Absent an evaluation of the risk of juror confusion and careful jury instructions, the testimony could not have 3 The small difference between what Lambatos actually said on the stand and the slightly revised version that the dissent would find unobjectionable shows that, despite the dissent s rhetoric, its narrow argument would have little practical effect in future cases. Prosecutors would be allowed to do exactly what the prosecution did in this case so long as their testifying experts testimony was slightly modified along the lines shown above. Following that course presumably would not constitute a prosecutorial dodge, subterfuge, indirection, the neat trick of sneak[ing] in evidence, or the countenancing of constitutional violations with a wink and a nod. See post, at 3, 16, 17, 12 (opinion of KAGAN, J.).

25 Cite as: 567 U. S. (2012) 19 Opinion of ALITO, J. gone to the jury. This case, however, involves a bench trial and we must assume that the trial judge understood that the portion of Lambatos testimony to which the dissent objects was not admissible to prove the truth of the matter asserted. 4 The dissent, on the other hand, reaches the truly remarkable conclusion that the wording of Lambatos testimony confused the trial judge. Were it not for that wording, the argument goes, the judge might have found that the prosecution failed to introduce sufficient admissible evidence to show that the Cellmark profile was derived from the sample taken from the victim, and the judge might have disregarded the DNA evidence. This argument reflects a profound lack of respect for the acumen of the trial judge. 5 To begin, the dissent s argument finds no support in the trial record. After defense counsel objected to Lambatos testimony, the prosecutor made clear that she was asking Lambatos only about her own testing based on [DNA] information that she had received from Cellmark. App. 56. Recognizing that Lambatos testimony would carry weight only if the underlying premises could be established, the judge noted that the issue is... what weight do you give the test [performed by Lambatos], not do you exclude it. Id., at 94. This echoes the old statement in Beckwith that an expert s opinion based on disputed premises might not go for much; but still it [is] admissible evidence. 1 Camp., at 117, 170 Eng. Rep., at 897. Both 4 We do not suggest that the Confrontation Clause applies differently depending on the identity of the factfinder. Cf. post, at (opinion of KAGAN, J.). Instead, our point is that the identity of the factfinder makes a big difference in evaluating the likelihood that the factfinder mistakenly based its decision on inadmissible evidence. 5 See post, at 14 (opinion of KAGAN, J.) ( I do not doubt that a judge typically will do better than a jury in excluding such inadmissible evidence from his decisionmaking process. Perhaps the judge did so here (emphasis added)).